Golf club head with top line insert

ABSTRACT

A golf club head having a recess located in a top portion thereof is described and claimed. The recess is located between the heel and the toe and extends toward the sole. The recess may be in the top line of the club head. An insert may be placed within the recess. The insert has a density that is less than the density of the club head body, and the insert preferably is a light-weight insert. The insert may include one or more damping materials. The recess removes material from the club head, which in turn may do one or more of the following: increase the overall size of the club head, expand the size of the club head sweet spot, lower the club head center of gravity, and/or produce a greater club head moment of inertia. Thus, the recess and insert produce a more forgiving and playable golf club. As an alternative to a recess, a thin protrusion may be provided at the top line of the club head and the insert provided with a corresponding groove to facilitate attachment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/843,622 filed on May 12, 2004, now pending, which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a golf club, and, more particularly, toa golf club head having a top line recess with a light-weight insert.

2. Description of the Related Art

Golf club heads come in many different forms and makes, such as wood- ormetal-type, iron-type (including wedge-type club heads), utility- orspecialty-type, and putter-type. Each of these styles has a prescribedfunction and make-up. The present invention relates to golf club headsthat have a predominantly solid material area located near the top ofthe club head.

Iron-type and utility-type golf club heads generally include a front orstriking face, a top line, and a sole. The front face interfaces withand strikes the golf ball. A plurality of grooves, sometimes referred toas “score lines,” is provided on the face to assist in imparting spin tothe ball. The top line is generally configured to have a particular lookto the golfer and to provide structural rigidity for the striking face.A portion of the face may have an area with a different type of surfacetreatment that extends fractionally beyond the score line extents. Someclub heads have the surface treatment wrap onto the top line. The soleof the golf club is particularly important to the golf shot because itcontacts and interacts with the ground during the swing.

In conventional sets of iron-type golf clubs, each club includes a shaftwith a club head attached to one end and a grip attached to the otherend. The club head includes a face for striking a golf ball. The anglebetween the face and a vertical plane is called the loft angle.

The set generally includes irons that are designated number 3 throughnumber 9, and a pitching wedge. One or more additional long irons, suchas those designated number 1 or number 2, and wedges, such as a lobwedge, a gap wedge, and a sand wedge, may optionally be included withthe set. Each iron has a shaft length that usually decreases through theset as the loft for each club head increases from the long irons to theshort irons. The overall weight of each club head increases through theset as the shaft length decreases from the long irons to the shortirons. To properly ensure that each club has a similar feel or balanceduring a golf swing, a measurement known as “swingweight” is often usedas a criterion to define the club head weight and the shaft length.Since each of the clubs within the set is typically designed to have thesame swingweight value for each different lofted club head or givenshaft length, the weight of the club head is confined to a particularrange.

The length of the shaft, along with the club head loft, moment ofinertia, and center of gravity location, impart various performancecharacteristics to the ball's launch conditions upon impact and dictatethe golf ball's launch angle, spin rate, flight trajectory, and thedistance the ball will travel. Flight distance generally increases witha decrease in loft angle. However, difficulty of use also increases witha decrease in loft angle.

Iron-type golf clubs generally can be divided into three categories:blades and muscle backs, conventional cavity backs, and modemmulti-material cavity backs. Blades are traditional clubs with asubstantially uniform appearance from the sole to the top line, althoughthere may be some tapering from sole to top line. Similarly, musclebacks are substantially uniform, but have extra material on the backthereof in the form of a rib that can be used to lower the club headcenter of gravity. A club head with a lower center of gravity than theball center of gravity facilitates getting the golf ball airborne. Sinceblade and muscle back designs have a small sweet spot, which is a termthat refers to the area of the face that results in a desirable golfshot upon striking a golf ball, these designs are relatively difficultto wield and are typically only used by skilled golfers. However, thesedesigns allow the skilled golfer to work the ball and shape the golfshot as desired.

Cavity backs are modern designs that move some of the club mass to theperimeter of the club by providing a hollow or cavity in the back of theclub, opposite the striking face. This produces a more forgiving clubwith a larger sweet spot. Having a larger sweet spot increases the easeof use. The decrease in club head mass resulting from the cavity alsoallows the size of the club face to be increased, further enlarging thesweet spot. The perimeter weighting created by the cavity also increasesthe club's moment of inertia, which is a measurement of the club'sresistance to torque, for example the torque resulting from anoff-center hit. These clubs are easier to hit than blades and musclebacks, and are therefore usable by less-skilled and beginner golfers.

Modern multi-material cavity backs are the latest attempt by golf clubdesigners to make cavity backs more forgiving and easier to hit. Some ofthese designs replace certain areas of the club head, such as thestriking face or sole, with a second material that can be either heavieror lighter than the first material. These designs can also contain deepundercuts, which stem from the rear cavity, or secondary cavities. Byincorporating materials of varying densities or providing cavities andundercuts, mass can be freed up to increase the overall size of the clubhead, expand the sweet spot, enhance the moment of inertia, and/oroptimize the club head center of gravity location. However, due toconstruction limitations or requirements, some of these designsinadvertently thicken the top portion of the club head. Still, theseimprovements make the multi-material cavity back design the easiest ofall styles to hit, and are ideally suited for the less adroit or novicegolfer.

As mentioned above, producing a low center of gravity in a club headincreases its playability. One of the ways to lower the center ofgravity is to lower the face profile of the head. However, this producesa club head with a bad aesthetic appearance. Another method of reducingthe club's center of gravity is to reduce the height of the hosel.However, there are disadvantages to reducing the hosel height, such as:reduced moment of inertia (since hosel mass is far away from the centerof gravity), shaft-bonding concerns, and the inability to customize theclub head via bending for loft/lie. In addition, many golfers dislikethe appearance of a club head that has a very small hosel.

SUMMARY OF THE INVENTION

The present invention relates to a golf club head having a body defininga front surface, a top line, a sole, a back, a heel, a toe, and a hosel.The top portion of the club head, preferably the top line, contains arecess therein located between the heel and the toe, and extendingtoward the sole. This recess removes material from the club head,allowing the opportunity to do one or more of the following: increasethe size of the overall club head, expand the size of the club headsweet spot, lower the club head center of gravity, and/or produce agreater moment of inertia measured about a vertical or horizontal axispassing through the club head center of gravity. The golf club head ofthe present invention preferably is an iron-type, a utility-type, or aputter-type golf club head.

An insert formed of a secondary material may be placed within therecess. The insert has a density that is less than the density of theclub head body, and the insert preferably is a light-weight insert. Thisallows the mass removed by the recess to be replaced in more desirouslocations on the club head, such as in the perimeter and/or toward thesole. The insert may contain one or more damping materials, such as aviscoelastic material, which have the added benefit of dissipatingvibrations that may be created during the golf shot. The incorporationof this secondary material provides improved feel and improved weightdistribution, enhancing performance of the club, while still maintainingan aesthetically pleasing overall head shape. The incorporation of thissecondary material also improves wearing of the heads over time sincethe viscoelastic material covers the top-toe area of the club, which isprimarily responsible for marks on the head due to club-to-club impactsas the clubs rest in a player's bag.

Instead of a recess, an extension may be provided at the top portion ofthe club head where relatively high density metallic material has beenremoved. The insert is attached to the extension.

DESCRIPTION OF THE DRAWING

The present invention is described with reference to the accompanyingdrawings, in which like reference characters reference like elements,and wherein:

FIG. 1 is a top view of a golf club head of the present invention;

FIG. 2 is a front view of the golf club head of FIG. 1;

FIG. 3 is a cross-sectional view of the golf club head of FIG. 1 takenalong lines 3-3;

FIG. 4 is a cross-sectional view of the golf club head of FIG. 1,including an insert, taken along lines 3-3;

FIG. 5 shows a first isometric view of the golf club head of FIG. 1;

FIG. 6 shows a second isometric view of the golf club head of FIG. 1;

FIG. 7 shows another golf club head of the present invention;

FIG. 8 shows a cross-sectional view of the golf club head of FIG. 7taken along line 8-8; and

FIG. 9 shows a cross-sectional view of another golf club head of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Other than in the operating examples, or unless otherwise expresslyspecified, all of the numerical ranges, amounts, values, andpercentages, such as those for amounts of materials, moments ofinertias, center of gravity locations, and others in the followingportion of the specification, may be read as if prefaced by the word“about” even though the term “about” may not expressly appear with thevalue, amount, or range. Accordingly, unless indicated to the contrary,the numerical parameters set forth in the following description andclaims are approximations that may vary depending upon the desiredproperties sought to be obtained by the present invention. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in any specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.FIG. 1 is a top view of a golf club head 1 of the present invention, andFIG. 2 is a front view of the golf club head 1. The golf club head 1includes a body 10 defining a front surface 11, a top line 12, a sole13, a back 14, a heel 15, a toe 16, and a hosel 17. The striking face ofthe front surface 11, which preferably contains grooves 18 therein, andthe sole 13 may be unitary with the body 10, or they may be separatebodies, such as inserts, coupled thereto. While the club head 1 isillustrated as an iron-type golf club head, the present invention mayalso pertain to a utility-type golf club head or a putter-type clubhead.

FIGS. 1 and 2 define a convenient coordinate system to assist inunderstanding the orientation of the golf club head 1 and other termsdiscussed herein. An origin O is located at the intersection of theshaft centerline CL_(SH) and the ground plane GP, which is defined at apredetermined angle from the shaft centerline CL_(SH), referred to asthe lie angle LA, and tangent to the sole 13 at its lowest point. AnX-axis is defined as a vector that is opposite in direction of thevector that is normal to the face 11 projected onto the ground plane GP.A Y-axis is defined as the vector perpendicular to the X-axis anddirected toward the toe 16. A Z-axis is defined as the cross product ofthe X-axis and the Y-axis.

The top portion of the club head 1 contains a recess 20 therein, locatedbetween the heel 15 and the toe 16 and extending toward the sole 13.Preferably, the recess 20 is located in the top line 12 of the club head1 and extends along the top line 12 from approximately 10% toapproximately 95% of the top line length. The top line length L_(TL) isdefined as the distance along the top line 12 from a point P₁ to a pointP₂. Point P₁ is defined as the intersection of the golf club head 1 anda plane that is offset 0.2 inch (L₁) from and parallel to a planedefined by the X-axis and the Z-axis tangent to the toe 16 at the toe'sfurthest point from the origin O along the Y-axis. Point P₂ is definedas the uppermost intersection of the club head 1 and a plane that isparallel to the plane formed by the shaft centerline CL_(SH) and theX-axis offset a distance of 0.3 inch (L₂) in a direction closer to thetoe 16. The recess 20 removes material from the club head 1, which canbe redistributed to other areas of the club head 1 to do one or more ofthe following: increase the overall size of the club head 1, expand thesize of the club head sweet spot, reposition the club head center ofgravity, and/or produce a greater moment of inertia (MOI) measured abouteither an axis parallel to the Y-axis or Z-axis passing through the clubhead center of gravity. Inertia is a property of matter by which a bodyremains at rest or in uniform motion unless acted upon by some externalforce. MOI is a measure of the resistance of a body to angularacceleration about a given axis, and is equal to the sum of the productsof each element of mass in the body and the square of the element'sdistance from the axis. Thus, as the distance from the axis increases,the MOI increases, making the club more forgiving for off-center hitssince less energy is lost during impact from club head twisting. Movingor rearranging mass to the club head perimeter enlarges the sweet spotand produces a more forgiving club. Moving as much mass as possible tothe extreme outermost areas of the club head 1, such as the heel 15, thetoe 16, or the sole 13, maximizes the opportunity to enlarge the sweetspot or produce a greater MOI. The recess 20 preferably has a volume ofapproximately 0.001 in³ to approximately 0.2 in³. In relative terms, therecess 20 preferably has a volume that is from approximately 0.5% toapproximately 10% of the volume of the body 10. The recess 20 preferablyhas a depth D from approximately 0.01 inch to approximately 0.25 inch,which may be a constant depth or a varying depth.

An insert 30 may be positioned within the recess 20. The insert 30,which may be either a preformed insert or cast in place within therecess 20, may be configured to matingly correspond to the recess 20.That is, the insert 30 may be formed and configured to match thecontours of the recess 20 and to substantially fill the recess 20.Alternatively, the insert 30 fills only a portion of the recess 20. Theinsert 30 has a density that is less than the density of the club headbody 10. Since the mass of the insert 30 is less than the mass removedby the recess 20, the extra mass may be replaced in more desirouslocations on the club head 1. These locations may include, for example,the club head perimeter and/or the sole 13. Alternatively, no additionalmass is added to the club head 1; only the recess 20 and the insert 30are used to enhance the playing characteristics of the golf club. Theinsert 30 preferably has a density from approximately 0.5 g/cm³ toapproximately 5 g/cm³, and is preferably less than the body density byat least 3 g/cm³. The net effect of creating the recess 20 and addingthe insert 30 lowers the club head center of gravity (CG₁ in FIG. 4) atleast 0.01 inch toward the sole 13, as compared to the center of gravitylocation of a club head without the recess 20 and the insert 30 (CG₂ inFIG. 4). That is, the golf club head 1 has a center of gravity locatedat least 0.01 inch from a center of gravity location for a substantiallysimilar golf club head without the recess 20 and the insert 30. Morepreferably, the club head center of gravity is lowered at least 0.025inch toward the sole 13. Additionally, the recess 20 and the insert 30increase the club head MOI measured about an axis parallel to the Z-axisand passing through the center of gravity by at least 20 gm·in². Thatis, the club head 1 has an increase in MOI measured about a verticalaxis passing through said center of gravity of at least 20 gm·in²compared to a substantially similar golf club head without the recess 20and the insert 30. Thus, the recess 20 and insert 30 produce a moreforgiving and playable golf club. FIGS. 5 and 6 show isometric views ofthe golf club head 1.

The insert 30 may contain one or more damping materials, which diminishvibrations in the club head, including vibrations generated during anoff-center hit. Preferred damping materials include those materialsknown as thermoplastic or thermoset polymers, such as rubber, urethane,polyurethane, butadiene, polybutadiene, silicone, and combinationsthereof. Energy is transferred from the club to the ball during impact.Some energy, however, is lost due to vibration of the head caused by theimpact. These vibrations produce undesirable sensations in both feel andsound to the user. Because the viscoelastic damping material of theinsert 30 is in direct contact with the metal club head (the vibratingbody), it serves to damp these vibrations, improving sound and feel.Typical hardness values for the insert 30 may include from 80 Shore A to50 Shore D. Typical densities for the insert 30 may include from 1.2-2g/cm³.

FIG. 7 shows another exemplary golf club head 2 of the presentinvention, and FIG. 8 shows a cross-sectional view of the golf club head2 taken along line 8-8. In this embodiment, material is removed from themetallic club head at the top line 12. Instead of forming a recess atthe top line 12, however, a thin protrusion 19 is provided. Metallicmaterial has been removed from the top portion of the club head asdescribed above, and a thin extension 19 is left in place. The insert 30has a groove corresponding to the protrusion 19. Thus, the viscoelasticmaterial can be fit onto the club head body 10. The insert 30 isattached to the casting, for example, through the use of an epoxy. Afixture with a cavity that matches the outer perimeter shape of the clubhead 1 should be used to hold the two pieces in place while the epoxydries. A preferred width A for the protrusion 19 is 0.06 in., thoughwider protrusions 19 may be used. This width ensures adequate structuralintegrity. Preferred heights for the protrusion 19 include 0.06 in. to0.25 in., though other heights may be used.

It is possible that there are variations in size of the metallicportions of the club heads 1, 2 caused during forming and polishing.These variations typically are larger than the variations in size due tomolding viscoelastic materials of the inserts 30. To aid in hiding anydiscrepancy between the two portions of the club head, a groove 32 maybe formed in the insert 30 the edges that are visible to the user oncethe two pieces have been put together. This groove 32 may be createdsimultaneously with the rest of the insert 30, or as a secondary step.The preferred width and depth of the groove 32 are 1 mm or less.

In the illustrated example of FIGS. 7 and 8, the protrusion 19 is formedin the center of the top line 12. Alternatively, the protrusion 19 canbe formed towards or at the front of the top line 12 or towards or atthe rear of the top line 12. The width B of the front portion of theinsert 30 may be zero, meaning the protrusion 19 forms the top portionof the face 11. Alternatively, the width B may be, for example, 0.03 to0.25 in. Similar to the width B, the width C of the rear portion of theinsert 30 may be zero, meaning the protrusion 19 forms the top portionof the back 14. Alternatively, the width C may be, for example, 0.03 to0.25 in. The height of the insert 30, measured along the longest portionthereof, preferably may be from 0.03 to 0.3 in.

A body's center of gravity is determined by its weight distribution.Mass added or removed directly on the center of gravity will have noeffect on the center of gravity's location. In contrast, mass added orremoved far away from the center of gravity will have the greatesteffect on moving the center of gravity. Removing mass from the highestareas of a club head will have the greatest effect on lowering thecenter of gravity. Adding the mass removed from the high areas to thebottom of the club head will further lower the center of gravity. Thetop line area and top-of-hosel area are the two highest vertical areasin relation to the ground plane on an iron-type head (when the head isat the address position). By removing the top line portion of the facefrom the casting and replacing it with a lightweight viscoelastic piece,anywhere from 20-50 grams are removed from the top of the head,depending upon the design of the viscoelastic piece. That weight isredistributed to the bottom portion of the club, lowering the center ofgravity even further versus that same club head constructed entirely ofa metallic material, such as steel.

MOI is also a property that is affected by mass distribution. Bodiesthat have mass distributed far from the center of gravity have higherMOI's about their center of gravity than bodies that have massconcentrated near their center of gravity. Removing the mass from thetop of the face lowers the MOI about the center of gravity with respectto certain axes. The axis of rotation that relates to an iron'sforgiveness is rotation in the heel-toe direction about the center ofgravity—an axis parallel to the Z-axis. A higher MOI about this axisindicates greater resistance to twisting on off-center hits and, thus,more forgiveness. By adding the mass removed from the top line 12 backinto the low-heel and low-toe areas of the club head, the reduction inMOI in the heel-toe direction due to removal of metallic material fromthe top line 12 is minimized.

Table 1 shows a comparison of center of gravity locations and MOI's fora 6-iron having a urethane insert 30 as shown in FIGS. 7 and 8 to asimilar club head formed completely of steel. Note that the measurementspresented in Table 1 do not include any weights that may be added to theclub head.

TABLE 1 6-iron with Urethane 6-iron with Top Line Steel Top Line Headmass 23.83 g 240.2 g Top Line mass 4.9 g 31.1 g Total mass 243.2 g 271.3g CG_(x) 1.355 in. 1.397 in. CG_(y) 0.766 in. 0.862 in. CG_(z) −0.478in. −0.533 in. I_(xx) 541 g · cm² 740 g · cm² I_(yy) 2588 g · cm² 2764 g· cm² I_(zz) 2832 g · cm² 3110 g · cm² k 1.173 in. 1.175 in. CG_(x),CG_(y), and CG_(z) are the x-, y-, and z-components of the center ofgravity location, respectively. I_(xx), I_(yy), and I_(zz) are the MOI'sabout the x-, y-, and z-axes, respectively. k is the spring constant.

Use of the insert 30 pictured in FIGS. 7 and 8 has the added benefit ofincreasing the durability of the club head 2. Over the course of play,clubs carried together in a bag are knocked together. These impactscreate marks on the club heads. The top-toe portion of the club is anarea that is likely to impact with other clubs. By making that area outof a softer material, the likelihood of creating marks on the head dueto club-to-club impacts is reduced.

FIG. 9 shows a cross-sectional view of another golf club head 3 of thepresent invention with the toe portion removed. In this embodiment,metallic material has also been removed from the top line 12 andreplaced with a light-weight viscoelastic insert 30. A protrusion 19 isalso provided in this club head 3, but unlike the previously discussedclub head 2 it is directed backward away from the face 11. The insert 30contains a groove corresponding to the protrusion 19. Attachment isfacilitated through the protrusion 19 and groove. The metallic facematerial extends to the upper most portion of the face 11 at the topline 12. Alternatively, the viscoelastic material may extend down thetop portion of the face 11, for example, up to 0.3 in.

While the preferred embodiments of the present invention have beendescribed above, it should be understood that they have been presentedby way of example only, and not of limitation. It will be apparent topersons skilled in the relevant art that various changes in form anddetail can be made therein without departing from the spirit and scopeof the invention. Thus the present invention should not be limited bythe above-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

1-12. (canceled)
 13. A golf club head comprising: a body formed of afirst material and having a front surface, a sole, a back, a heel, atoe, and a top; a protrusion extending away from the body at the top,wherein the protrusion is directed backwards and away from the face whenthe club head is at address; and an insert formed of a second materialand coupled to the protrusion.
 14. The golf club head of claim 13,wherein the protrusion is located near, and substantially parallel to, atop line of the club head.
 15. The golf club head of claim 13, whereinthe first material has a first density and the second material has asecond density that is less than the first density.
 16. The golf clubhead of claim 15, wherein the first density is greater than the seconddensity by at least 3 grams per cubic centimeter.
 17. The golf club headof claim 15, wherein the second density is within a range from about 0.5grams per cubic centimeter to about 5 grams per cubic centimeter. 18.The golf club head of claim 13, wherein the second material is avibration damping material.
 19. The golf club head of claim 13, whereinthe first material extends to the upper-most portion of the face whenthe club head is at address.
 20. The golf club head of claim 13, whereina moment of inertia—measured about a vertical axis passing through acenter of gravity of the club head when the club head is at address—isat least 20 gm·in² greater than a similarly-measured moment of inertiaof a substantially similar golf club head in which the second materialis replaced with the first material.
 21. The golf club head of claim 13,wherein: the body has a first volume; the insert has a second volume;and the second volume is from 0.5% to 10% of the first volume.
 22. Aniron-type golf club head comprising: a body made with a first materialand defining a front portion, a top portion, a sole portion, a heelportion, a toe portion, and a hosel, the body comprising an extension atthe top portion and extending backwards from the club head; and aninsert made with a second material and attached to the extension. 23.The club head of claim 22, wherein the insert comprises a groove and isattached to the body at an interface between the groove and theextension.
 24. The club head of claim 22, wherein the top portion andthe insert cooperate to define a substantially smooth upper surface ofthe club head.
 25. The club head of claim 22, wherein the club head is acavity-back iron style club head comprising a cavity in a back of theclub head.
 26. The club head of claim 25, wherein the front portion hasa first side providing a ball striking face and an opposed second sideproviding a wall of the cavity.
 27. The club head of claim 25, whereinthe cavity is open to the back but otherwise substantially surrounded bythe front portion, the sole portion, the heel portion, the toe portion,and the insert.
 28. The club head of claim 25, wherein the secondmaterial is less dense than the first material.
 29. The club head ofclaim 25, wherein the insert makes contact with the body along an upperstrip that is above the extension member and a lower strip that is belowthe extension member when the club head is at address.
 30. The club headof claim 25, wherein the insert extends along the top portion from theheel portion to the toe portion.
 31. The club head of claim 30, whereinthe insert wraps around and substantially conceals the extension member.32. The club head of claim 31, wherein the first material extends to theupper most portion a face of the club head at a top line of the clubhead.
 33. The club head of claim 32, wherein the second material meetsthe first material substantially along the top line.
 34. A cavity-backediron-type golf club head comprising: a body comprising a front portion,a top portion, a sole portion, a heel portion, a toe portion, a hosel,and a projection jutting back from the top portion; and a low densityinsert covering at least a portion of the projection and cooperatingwith the heel portion, the toe portion and the sole portion to define acavity open to a back side of the club head.
 35. The club head of claim34, wherein the low-density insert makes contact with the body above,along, and below the projection when the club head is at address. 36.The club head of claim 35, wherein the a back surface of the frontportion defines a wall of the cavity.
 37. The club head of claim 36,wherein an edge of the insert is adjacent an edge of the top portionalong a top line of the club head.
 38. The club head of claim 34,wherein: the low density insert extends along the top portion from theheel portion to the toe portion and makes contact with the top portionabove and below the projection, and the club head comprises a cavitythat is open to a back of the club head but otherwise substantiallysurrounded by the front portion, the sole portion, the heel portion, thetoe portion, and the low density insert,.